Plant diseases are one of the major limiting factors to shrink agricultural production and farmers use high amounts of toxic chemicals to control plant diseases, unaware of the fact that balanced nutrition can check diseases to an extent. Plant nutrients may affect disease susceptibility through plant metabolic changes, thereby creating a more favorable environment for disease development. When a pathogen infects a plant, it alters the plant's physiology, particularly with regard to mineral nutrient uptake, assimilation, translocation, and utilization. They may also interfere with translocation or utilization of nutrients, inducing nutrient deficiencies or toxicities. The resulting deficiencies may lead to secondary infections by other pathogens. Ionomics, emerged as the study of the ionome (mineral nutrient and trace element composition representing inorganic component of cell), depends on the growth, physiology and genetic modifications of the plant cells. Nutrients are essential for the metabolism of crop plants hence growth and yield as well as can be considered as an important component in plant-disease interactions. Because of the complex interaction between disease, nutrient and environment, vivid information is required about how a particular nutrient is actually working in crop plants to develop a strong defense system. Knowledge on plant nutrition thus deserves a priority for disease management as a part of integrated crop production system, because balanced nutrient supply ensures optimal plant growth and is usually considered optimal for disease resistance as well. Thus, this article focuses on the information regarding management of plant diseases (fungal, bacterial and viral) by balanced application of nutrients with a special emphasis to primary (N, P, K) and secondary (Ca, Mg, S) nutrients.

We measured the long-term (28 years) sustainability of rice-wheat cropping system under integrated nutrient management practices emphasizing the trends in grain yields, sustainable yield index (SYI) and nutrient budgeting. The data of long-term experiment revealed that grain yield of both rice and wheat declined under control and sub-optimal fertilizer inputs (50% or 75% recommended fertilizer NPK). Negative yield trend (slope) was observed in control plots for rice (-0.0296) and wheat (-0.0070); whereas positive yield trend was observed under treatments receiving organic supplements. The SYI values indicate that rice yields are more sustainable than wheat. Data on apparent nutrient balance showed a deficit of N (-42.2 kg/ha/year), P (-9.1 kg/ha/year) and K (-52.2 kg/ha/year) under control plots. Surprisingly, there was net depletion of K under the organic supplemented plots. Correlation study revealed that apparent balance of K was negatively correlated with SYI (r = -0.921 for rice; r = -0.914 for wheat) and yield slope (r = -0.870 for rice; r = -0.896 for wheat). If the trend of K imbalance is not reversed, the potential to improve N and P fertilizer use efficiency and crop yields will be limited.

Using phytotron growth chambers, a short-term pot experiment under nonlimiting water condition was conducted to investigate the individual and interactive effects of elevated carbon dioxide (650 ± 10 lmol mol )1 vs. ambient), temperature (3°C above ambient vs. ambient) and different levels of urea-N (control, 100 % N and 200 % N of recommended dose) on growth and yields of wheat crop and changes in potential nitrogen mineralization (PNM), nitrification and denitrification activities, microbial biomass carbon (MBC), nitrogen (MBN), dissolved organic carbon (DOC), and nitrifying and denitrifying organisms in a semiarid Inceptisol. The plant parameters (root, shoot and grain) responded positively (10-23 %) to elevated CO 2 and negatively ()17 to )38 %) to higher temperature. Interactive effect of elevated CO 2 and temperature caused a negligible impact on root, shoot (%)5 %) and grain yields of wheat. Soil NH þ 4 -N content was not affected, but NO À 3 -N was reduced significantly. Nitrate reductase activity was decreased by 14-20 % at elevated CO 2 . There was positive effect of elevated temperature on PNM (+9-16 %), whereas negative effects were observed for potential nitrification activity (PNA), MBC, MBN and DOC. Elevation of atmospheric CO 2 or temperature did not affect the population of ammonia (AOB) and nitrite oxidizers (NOB), but elevation of CO 2 has decreased the population of denitrifiers by 4-14 %.

Modern agricultural innovations with nanomaterials are now being applied in every sphere of agriculture. However, their interaction with soil microbial processes is not being explored in detail. This initiative was undertaken to understand the effect of metal-oxide nanoparticles with heat stress in soil. Metal-oxide nanoparticles, zinc oxide (ZnO), and iron oxide (Fe2O3) (each at 10 and 40 mg kg−1 w/w) were mixed into uncontaminated soil and subjected to heat stress of 48 °C for 24 hours to assess their effect on soil biological indicators. The resistance indices for the acid (ACP), alkaline phosphatase (AKP) activity, and fluorescein diacetate hydrolyzing (FDA) activity (0.58 to 0.73, 0.58 to 0.66, and 0.42 to 0.48, respectively) were higher in the presence of ZnO nanoparticles as compared to Fe2O3 nanomaterials, following an unpredictable pattern at either 10 or 40 mg kg−1 in soils, except dehydrogenase activity (DHA), for which the activity did not change with ZnO nanomaterial. An explicit role of ZnO nanomaterial in the revival pattern of the enzymes was observed (0.20 for DHA, 0.39 for ACP, and 0.43 for AKP), except FDA, which showed comparable values with Fe2O3 nanomaterials for the following 90 day (d) after stress. Microbial count exhibiting higher resistance values were associated with Fe2O3 nanoparticles as compared to ZnO nanomaterials, except Pseudomonas. The recovery indices for the microbial counts were higher with the application of Fe2O3 nanomaterials (0.34 for Actinobacteria, 0.38 for fungi, 0.33 for Pseudomonas and 0.28 for Azotobacter). Our study emphasizes the fact that sensitive microbial indicators in soil might be hampered by external stress initially but do have the competency to recover with time, thereby reinstating the resistance and resilience of soil systems.

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